Field of the Invention
The present invention relates to a toner that is used in image-forming methods such as electrophotographic methods, electrostatic recording methods, and toner jet methods.
Description of the Related Art
There has been demand in recent years for lower energy consumption in, for example, copiers and printers. An effective means for doing this is to reduce the set temperature in the fixing member. However, this then requires, as a property of the toner, that softening occurs at lower temperatures. In addition, copiers and printers are now being used in diverse regions and environments, and it is therefore necessary to also provide storability at high temperatures (heat-resistant storability). The use of crystalline materials has been investigated for these problems.
A property of crystalline materials is that they exhibit almost no change in viscosity up to the melting point and then melt all at once when the melting point is exceeded (a sharp melt property). By introducing a crystalline material into a toner, the glass transition temperature (Tg) of the binder is lowered by heating during fixing, without causing a deterioration in the heat-resistant storability, and the fixing performance (low-temperature fixability) can be improved at a low set temperature.
Japanese Patent Application Laid-open No. 2006-106727 provides a toner that uses a crystalline material. However, when a toner as taught here undergoes melting during fixing, the binder resin and the crystalline material may end up separating, and the pigment dispersibility in the fixed image then declines and the appearance quality of the image undergoes a decline. For the same reason, the effect of reducing the glass transition temperature (Tg) of the binder resin during fixing may also not be satisfactory.
To respond to this problem, Japanese Patent Application Laid-open No. 2012-128071 proposes a composite resin of a crystalline material and an amorphous material. Here, an amorphous segment is introduced through graft polymerization into a crystalline material. However, from the standpoint of the production method, when the introduction of a large amount of the amorphous component is sought, adverse effects occur such as an increase in the molecular weight due to crosslinking reactions, and as a consequence the problem at issue is not solved.
Also in view of this problem, Japanese Patent Application Laid-open No. S62-273574 proposes the use of a crystalline block resin and amorphous block resin as the binder resin. However, when such a toner is used, since the principle binder resin is the block resin, the block resin that is the crystalline material is present at the toner surface. Since a property of crystalline materials is that they are brittle with respect to external forces, when continuous high-speed printing is performed a satisfactory durability is not obtained, as compared with the highly durable styrene-acrylic binder resins, and this becomes a factor in causing image defects such as, for example, development stripes.